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Serpens CaputSerpens Cauda
Meaning in Englishthe Snake
the Snake's Headthe Snake's Tail
Right ascension15.5 h18.3 h
Visible to latitudeBetween 80° and -80°
On meridian9 p.m., June 309 p.m., August 5
 - Total
Ranked 23rd
637 sq. deg.
429 sq.deg.208 sq.deg.
Number of stars with
apparent magnitude < 3
Brightest star
 - Apparent magnitude
Unukalhai (α Ser)
Meteor showers
Bordering constellations

Serpens (the snake) is one of the 88 modern constellations, and was also one of the 48 listed by Ptolemy. Among the modern constellations it is unique in being split into two pieces, Serpens Caput (representing the head of the snake) to the west and Serpens Cauda (representing the tail) to the east. Between these two pieces lies the constellation of Ophiuchus, the serpent bearer.

Table of contents
1 Notable features
2 Notable deep-sky objects
3 Mythology

Notable features

Since Serpens is regarded as being one constellation despite being split into two halves, the ordering of Bayer designations goes in order of brightness among both constellations.

Only one of the stars in Serpens is brighter than third magnitude, so the constellation is not easy to perceive. α Serpentis, named Unukalhai, is in Caput. δ Serpentis, also in Caput, is a double star only 27 light-years from Earth. θ Serpentis, in Cauda, is also double.

Stars in Caput include α, β, γ, δ, ε, ι, κ, λ, μ, π, ρ, σ, τ, χ and ω Serpentis. Stars in Cauda include ζ, η, θ, ν, ξ, and ο Serpentis.

Notable deep-sky objects

M5, a globular cluster approximately 8° southwest of α Serpentis in Caput, is among the most beautiful in the sky.

M16 is a young open cluster associated with the Eagle Nebula, a diffuse nebula which is a region of current star foermation in Serpens Cauda.

Part of the Milky Way passes through Serpens Cauda.


Serpens is the snake being grasped by Ophiuchus, the Snake-Handler, q.v. Originally they were all one very large constellation.